An Overview

Biography

Anny is a recent graduate of Smith College with bachelors in Geoscience and minor in Government. Her love for geology sparked after spending most of her summers exploring the mountainous landscape of New England and even having the opportunity to adventure to the glaciers of the Northern Cascades. Anny is particularly interested in reconstructing paleoclimates using sedimentology. This summer, Anny did her research at the University of Washington, looking at how normal earthquake events interact with slow slip earthquakes in the Southern Cascadia Subduction Zone.

Abstract

The Effect of Earthquakes on Episodic Tremor and Slip Events on the Southern Cascadia Subduction Zone

Episodic tremor and slip (ETS) have been a topic of focus during the last decade and there is much to be learned about these enigmatic events. When oceanic plates subduct into the mantle, friction with the overriding plate causes a stick-slip behavior within the megathrust (where the plates converge), which pulls the upper plate down until it springs back up, resulting in a destructive earthquake that originates from the shallow locked zone (Brudzinski et al., 2007). At great depth, the plate interface is believed to slide freely due to high temperatures. At intermediate depths on the plate interface (~40 km), transient fault slip is observed in the form of ETS events (Gomberg, 2010). These ETS events occur regularly (every 11-24 months), and have a longer duration than normal earthquakes. Researchers have been documenting slow slip events through data obtained by continuously running GPS stations in the Pacific Northwest (Gomberg, 2010). The interaction of earthquakes and ETS can provide constraints on the strength of the fault and the level of stress needed to alter ETS behavior. Earthquakes can trigger slow ETS events, but the connection between these events and earthquake activity is less understood. We previously hypothesized that ETS events are affected by earthquakes and could result in a shift in the recurrence interval of ETS events. ETS events were cataloged using GPS time series and seismic tremor data provided by PANGA in Southern Cascadia for stations YBHB and DDSN to look for evidence of change from three offshore earthquakes, occurring near the Mendocino Triple Junction with magnitudes of 7.2 in 2005, 6.5 in 2010, and 6.8 in 2014. Our results showed that the recurrence rate of ETS in stations YBHB and DDSN was not altered by the three earthquake events. This is likely due to the due to the difference in orientation of the earthquake events from the receiver fault.